I've had severe BGA issues. I can manually remove it all (as in I can't see any left) and a few days later it's back all over the tank. I've considered the often repeated advice of a 3 day blackout, but what I don't understand is how this helps. If you remove it all manually (which is quite easy to do) isn't this the same as what a blackout would achieve? The blackout would kill off all the BGA, but then it would be immediately reintroduced to the tank ( as it's so common). Is a blackout only useful when you have something like a dutch tank where the BGA is impossible to manually remove?